The single-car crash that killed disabled Petaluma teenager Danny Cox in August was ruled a suicide Friday by the Marin County Sheriff's Office.

Cox, 19, died Aug. 7 after his Dodge Magnum wagon struck an oak tree next to Highway 101 near Olompali State Historic Park.

The former Petaluma High track star had just started to drive weeks earlier after suffering devastating injuries in a shallow-water diving accident the previous August.

The accident left him paralyzed below the chest and he was dependent on others for many of life's necessities. He was able to drive thanks to a modified car he could control with his hands.

Witnesses to the crash said Cox was traveling between 60 and 70 mph before hitting the tree. No skid marks were found to indicate he attempted to brake.

The findings by the Marin County Coroner and the Marin office of the CHP concluded that Cox's death was a suicide, but provided no explanation. Officials were not available for comment Friday.

His mother, Maureen McGowan, dismissed the notion her son wanted to die, though she alluded to the toll of the diving accident a year earlier.

"A broken neck took the life of my son," she said. "He died as the result of catastrophic injuries from the diving accident, absolutely that's what killed him."

Prior to the accident, Cox had been a gifted long-jumper, leaping 21 feet and placing 11th in the state high school sectionals in Berkeley.

After graduating from high school in 2010, he was on the cusp of starting his first semester at Santa Rosa Junior College, where he planned to pursue a career in firefighting, when the spinal injury turned his world upside down.

Cox's plight moved the hearts of many. His family, friends, teammates and former classmates rallied behind him, as did the greater Petaluma community, which raised tens of thousands of dollars to help with mountainous medical costs.

His death left many stunned. More than 1,000 people attended a rememberance for him at Petaluma High's track and football field a week after his death.

— By Sam Scott, The Press Democrat